Many industrial tools require electric motors which are relatively large consumers of electric energy. Some tools are used by many persons sharing the same work area. As one worker shuts down a machine and leaves the area, another worker walks up and turns it on again. Quite often the tool motor has not had a chance to shed the residual heat from its initial startup. As a result, the frequent re-starting causes abnormally high running temperatures, and premature need for expensive maintenance. Furthermore, the cost of such premature wear and tear uses a great deal of electricity. In all such cases, the metered amount of energy consumed by the motor is greater than the rated energy consumption under normal loading.
Some typical examples are: dryers at the exits of automatic car washes, belt sanders, electric presses, and electric bending brakes.
Until now, the standard solution is to employ an intelligent electronic device (IED) such as a programmable logic controller (PLC) between the start/stop switch and the motor's own load relay. These devices would be programmed to do one of two things: 1) Delay the reaction time to turn off the load relay a preset number of seconds, then turn off the motor. If the motor is turned back on before the PLC times out, the delay is interrupted. 2) Calculate the length of time the motor is being turned off, then compare it against a fixed preset length of time. If the "off-time" is shorter than the preset, the motor is kept running until the opposite is true. The preset must be manually calculated for each motor, and does not dynamically adjust as the motor ages.
The IED or PLC needed for this type of intervention is too complex for most electricians to employ due to the knowledge required for programming. Also, the costs of these devices still rivals the cost of the motor replacement. Unless a great deal is known about the motor, and PLC programming, there is no way to know if the solution is cost feasible until a great deal of time has passed and sufficient quantitative billing information is gathered.
There is a need for a device which addresses these problems.
It is an object of the invention to provide alternative means of entering calculated numerical information into computers.